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PubMed1995

Failures in ridge reconstruction with hydroxyapatite. Analysis of cases and methods for surgical revision.

Misuse of hydroxyapatite for ridge reconstruction leads to problems in denture construction. The object of this article is to analyze cases that have failed to provide acceptable results and to discuss methods for surgical revision. The group under study was made of 30 patients treated originally in different centers (with one exception) with 34 attempts at ridge reconstruction for the 27 mandibular cases and 3 maxillary ones. Only two mandibular cases received a skin graft. Three major problems were identified: (1) improper location of hydroxyapatite over the vestibular instead of the lingual or palatal sides of the ridge (27 of 30 cases); (2) poorly defined ridge form (26 of 30 cases); and (3) submucosal hydroxyapatite extrusion (15 of 30 cases). Splints or binding agents did not prevent these complications. Mandibular revision was accomplished by adding hydroxyapatite over the old material and onto the lingual side of the ridge. At a second stage, the floor of the mouth was lowered. As the vestibule was extended, material in excess was removed before skin graft application. Maxillary revision involved material removal from the vestibular side to allow the lining mucosa of the vestibule to return to a normal position.

Alveolar Ridge Augmentation↗
PubMed1995

Accumulation of technetium-99m methylene diphosphonate. Conditions affecting adsorption to hydroxyapatite.

Experiments were carried out to explore the mechanism of technetium-99m methylene diphosphonate (99mTc-MDP) adsorption with various calcium compounds including hydroxyapatite powder. 99mTc-MDP adsorption to hydroxyapatite was markedly inhibited by the addition of either pyrophosphate or methylene diphosphonate (MDP). Moreover, adsorbed 99mTc-MDP was partly removed by rinsing with pyrophosphate solution. Adsorption was pH-dependent and was inhibited by univalent cations, adenosine triphosphate solution, and guanosine triphosphate. Adsorption was most apparent to hydroxyapatite and calcium pyrophosphate and was less marked for the other calcium compounds tested. It is suggested that 99mTc-MDP adsorption is affected by the hydroxyapatite crystalline structure and environmental factors such as pH and the presence of phosphates, calcium compounds, and various cations.

Adsorption↗
PubMed1999

Characterization of porous hydroxyapatite.

Hydroxyapatite has been considered for use in the repair of osseous defects for the last 20 years. Recent developments have led to interest in the potential of porous hydroxyapatite as a synthetic bone graft. However, despite considerable activity in this field, regarding assessment of the biological response to such materials, the basic materials characterization is often inadequate. This paper documents the characterization of the chemical composition, mechanical integrity, macro- and microstructure of a porous hydroxyapatite, Endobon (E. Merck GmbH), intended for the bone-graft market. Specimens possesed a range of apparent densities from 0.35 to 1.44 g cm(-3). Chemical analysis demonstrated that the natural apatite precursor of Endobon was not converted to pure hydroxyapatite, but retained many of the ionic substituents found in bone mineral, notably carbonate, sodium and magnesium ions. Investigation of the microstructure illustrated that the struts of the material were not fully dense, but had retained some traces of the network of osteocyte lacunae. Macrostructural analysis demonstrated the complex inter-relationship between the structural features of an open pore structure. Both pore size and connectivity were found to be inversely dependent on apparent density. Furthermore, measurement of pore aspect ratio and orientation demonstrated a relationship between apparent density and the degree of macrostructural anisotropy within the specimens, while, it was also noted that pore connectivity was sensitive to anisotropy. Compression testing demonstrated the effect of apparent density and macrostructural anisotropy on the mechanical properties. An increase in apparent density from 0.38 to 1.25 g cm(-3) resulted in increases in ultimate compressive stress and compressive modulus of 1 to 11 MPa and 0.2 to 3.1 GPa, respectively. Furthermore, anisotropic high density (> 0.9 g cm(-3)) specimens were found to possess lower compressive moduli than isotropic specimens with equivalent apparent densities. These results underline the importance of full structural and mechanical characterization of porous ceramic implant materials.

Journal Article↗
PubMed1998

Thin hydroxyapatite coatings via sol-gel synthesis.

Production of hydroxyapatite coatings using an alkoxide-based sol-gel route requires control of solution aging time and heating schedule. 31P nuclear magnetic resonance spectroscopy was used to investigate the changes during aging of the sol and thermal gravimetric analysis employed to study the behavior of the xerogels as a function of temperature, while final products were determined using X-ray diffraction. Results from 31P nuclear magnetic resonance spectroscopy and thermal analysis revealed that sols must be aged for at least 24 h to complete the reaction of the two reactants. Deposition of the sol for coating production will then yield monophasic hydroxyapatite. Coatings produced from sols aged for less than 24 h yielded calcium oxide in addition to hydroxyapatite. Prefiring is necessary to remove most of the residual organic materials. Final heating up to 800 degrees C produces crystallization at 550 degrees C and removal of the remaining organic constituents for the formation of a thin hydroxyapatite layer.

Journal Article↗
PubMed2004

Effect of particle morphology and polyethylene molecular weight on the fracture toughness of hydroxyapatite reinforced polyethylene composite.

Fracture toughness testing has been performed on hydroxyapatite-polyethylene composites. Sintered and unsintered grades of hydroxyapatite and two grades of high-density polyethylene were used to make 40 vol % hydroxyapatite composites. Compact tension testing was performed at both room temperature and at 37 degrees C and at three strain rates. The effect of increasing the loading rate from 2 to 200 microm s(-1) was to increase the fracture toughness. Increasing the testing temperature or decreasing the surface area of the reinforcing particles also increased the fracture toughness. However, using a lower molecular weight, injection moulding, grade of polyethylene reduced the fracture toughness. Thus for higher fracture toughness, a low surface area sintered hydroxyapatite in a high-molecular weight polyethylene is required.

Biocompatible Materials↗
PubMed1997

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Part III. Evaluation of autogenous bone combined with porous hydroxyapatite.

The aim of this study was to evaluate clinically, histologically, and histometrically the use of autogenous bone combined with porous hydroxyapatite (Interpore 200) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted. After a healing period of 3 months, maxillary sinus augmentation procedures were performed in each monkey, and the sinuses were grafted with autogenous bone from the monkeys' tibia mixed in a 3:1 ratio with porous hydroxyapatite. At the same time, 2 pure titanium plasma-sprayed IMZ cylinder implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received similar treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants unloaded group and delayed implants unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation. The porous hydroxyapatite granules appeared integrated with the newly formed bone. Histometric analyses revealed that delayed implant placement resulted in a greater amount of direct mineralized bone-to-implant contact in the augmented area than the simultaneous implant placement. Furthermore, the percentage of direct mineralized bone-to-implant contact was far more significant in the residual bone than in the augmented area. It was concluded that the autogenous bone/porous hydroxyapatite graft combination enhanced bone formation and mineralized bone-to-implant contact in the augmented sinuses and that the delayed implant placement may be favorable for sinus augmentation procedures.

Animals↗
PubMed1997

Maxillary sinus augmentation using different grafting materials and osseointegrated dental implants in monkeys. Part II. Evaluation of porous hydroxyapatite as a grafting material.

The aim of this study was to evaluate clinically, histologically and histometrically the use of porous hydroxyapatite (i.e. Interpore-200) as a bone grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (i.e. Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted and the remaining bone between the alveolar crest and the bottom of the sinus was reduced to 3-4 mm. After 3 months, maxillary sinus augmentation procedures were performed on one side of the jaws in each monkey, and the sinuses grafted with the porous hydroxyapatite. Two IMZ titanium plasma-sprayed cylinder implants were then immediately placed into the augmented sinus (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice). The contralateral side of each monkey received the same treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants-unloaded group and delayed implants-unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologic analysis demonstrated a significant amount of new bone formation in the augmented sinuses. Porous hydroxyapatite graft particles appeared to be integrated to the new bone. The percentage of direct mineralized bone-to-implant contact in the augmented area was greater on the delayed-placed implants than on the simultaneously-placed implants. Also, the percentage of direct mineralized bone-to-implant contact was greater in the residual bone than in the augmented area. It was concluded that this porous hydroxyapatite bone graft enhanced bone formation and bone-to-implant contact in the augmented sinuses and that the delayed implant placement in combination with the sinus augmentation procedure appears to result in a higher percentage of direct mineralized bone-to-implant contact.

Alveolar Process↗
PubMed1999

Synthetic hydroxyapatite orbital implants: a clinical and MRI evaluation.

PURPOSE: Coralline hydroxypatite orbital implants have been used since the 1980s. More recently, synthetic hydroxyapatite orbital implants have been used, in both primary and secondary orbital implantation surgery. The implant may be drilled and pegged, if required, after adequate vascularisation of the implant has occurred. In this study we evaluated the clinical results and vascularisation of synthetic hydroxyapatite orbital implants. METHODS: Twelve consecutive patients who had synthetic hydroxyapaptite orbital implants were evaluated clinically and 8 of these patients had orbital magnetic resonance imaging (MRI) scans with intravenous gadolinium performed at least 9 months post-operatively to assess vascularisation of the implant. Six patients had primary orbital implants at the time of enucleation and 6 patients had secondary implants. RESULTS: No significant complications occurred following insertion of the synthetic hydroxyapatite orbital implants. All patients reported cosmetic satisfaction with the results of surgery. MRI scans revealed inhomogeneous enhancement in 3 of the 4 patients receiving primary implants. All patients with secondary implants and 1 patients who had a primary implant had moderate to large areas of poor enhancement in the implant. CONCLUSION: Synthetic hydroxyapatite implants gave good clinical results but variable vascularisation occurs, especially with secondary implants.

Adolescent↗
PubMed1997

Mastoid obliteration with hydroxyapatite--the value of high resolution CT scanning in detecting recurrent cholesteatoma.

Mastoid obliteration carries a risk of enclosing cholesteatoma within the mastoid cavity. Using temporal bones obliterated with either muscle or hydroxyapatite granules, the value of high resolution CT scanning in the early detection of 'epithelial pearls' was studied. The results showed that scanning was effective in detecting small epithelial pearls within the cavity obliterated with hydroxyapatite, but not so effective when muscle was used. This is explained by the difference in the CT density between epidermoid cysts and hydroxyapatite allowing the cysts (dark shadows) to be identified easily within a white background. The authors also studied scans performed on 31 ears following mastoid obliteration with hydroxyapatite. There was no residual cholesteatoma in the obliterated area but there was an area of abnormality identified within the obliterated area in one patient due to a cholesterol granuloma.

Biocompatible Materials↗
PubMed1999

Late infection of hydroxyapatite orbital implants.

BACKGROUND: Exposure and minor complications of hydroxyapatite orbital implants are common. Infection appears to be rare and fibrovascular ingrowth into hydroxyapatite implants may make infection and extrusion less likely than with other types of orbital implant. METHODS: We describe three cases of chronic low-grade infection of hydroxyapatite implants, occurring late after apparently uncomplicated surgery, with tiny or inapparent areas of conjunctival loss or exposure. RESULTS: Two of the three cases grew Staphylococcus oureus on culture. All three implants ultimately needed to be removed. A characteristic histological pattern was seen, with abrupt transition between vascularized and abscessed implant. CONCLUSIONS: Chronic infection of hydroxyapatite implants can occur late, in the absence of large conjunctival defects, or other obvious risk factors. While exposure of the implant to pathogens through a breach in the conjunctiva may have been a factor, it appeared that the infection may have arisen in an avascular portion of the implant prior to the conjunctival breakdown in one or more of these cases.

Aged↗
PubMedDate not supplied

Hydroxyapatite augmentation for bone atrophy in total ankle replacement in rheumatoid arthritis.

Although total ankle replacement is routinely used for rheumatoid arthritis of the ankle, it has been hampered by early implant failures such as loosening and subsidence of the tibial component due to poor bone quality. To prevent this complication, total ankle replacement augmented by a specially designed hydroxyapatite coating was used in 14 patients (16 feet). Patients were reviewed after an average follow-up of 23.1 months, and the mean clinical rating scale significantly improved from 30.7/100 points preoperatively to 65.9/100 at final follow-up, especially with respect to pain relief. Radiographs taken immediately postoperatively and at final follow-up were analyzed for the position and sinking of the tibial component. The position was evaluated by measurement of the alpha and beta angles, formed by the tibial long axis and tibial component on anteroposterior and lateral radiographs, respectively. The mean alpha and beta angles were 87.4 degrees and 79.3 degrees postoperatively and 87.7 degrees and 81.0 degrees at final follow-up, respectively. No significant change was noted in either angle between the immediate postoperative views and at final follow-up, and no significant subsidence was noted. Radiographs were also assessed for the presence of a lucent zone: 1 case demonstrated a clear zone between hydroxyapatite and bone, 9 cases between hydroxyapatite and the tibial component, and 6 cases between the tibial component and bone. These results suggest that hydroxyapatite helps to secure implant fixation firmly to the bone, making it a useful augmentation for tibial bone atrophy in total ankle replacement for rheumatoid arthritis.

Aged↗
PubMed1994

[Orbital implants of coralline hydroxyapatite as eye replacement after enucleation].

BACKGROUND During the last two decades, hydroxyapatite has become popular as alloplastic material for bone replacement in orthopedic and dental surgery. We investigated prospectively the feasibility of hydroxyapatite spheres as replacement of enucleated eyes. PATIENTS AND METHODS Thirty-three consecutive patients entered a prospective study designed to evaluate the results obtained after either primary (n = 26) or secondary (n = 7) implantation of a hydroxyapatite sphere as replacement of the enucleated eyeball. Each patient was examined preoperatively, 1, 2, and 4 months after surgery, as well as every 6 months thereafter. At each examination time the motility of both coralline sphere and overlying cosmetic prosthesis was evaluated and the conjunctival sac was carefully examined at the slit-lamp. RESULTS The postoperative follow-up averaged 10.5 months for the primary implantations and 7.2 months for the secondary implantations. Two implants had to be removed because of infection unresponsive to antibiotic treatment. Defects in the conjunctiva overlying the implant necessitated wound revision in two cases. A buccal mucosal graft was performed in two additional ones. A temporary cosmetic prosthesis could be fitted in all but two of the remaining patients as early as 3 weeks after surgery. Motility of at least 3 mm in all directions could be obtained in 31 cases. CONCLUSION Our study demonstrated that satisfactory motility and good biocompatibility can be achieved, at least in the medium term, with implantation of coralline hydroxyapatite spheres.

Adolescent↗
PubMed2002

Histologic evaluation of a threaded hydroxyapatite-coated root-form implant located at a dehisced maxillary site and retrieved from a human subject: a clinical report.

This clinical report describes the microscopic analysis of a threaded hydroxyapatite-coated root-form implant retrieved from an 89-year-old subject after 10 months of service. The implant was never loaded and was removed because it was nonrestorable. Clinically, the buccal area of the implant was covered by soft tissue, whereas the palatal side was covered by bone. Light microscopic evaluation revealed tight contact between hydroxyapatite and bone with no sign of coating dissolution. Osteocytes were present, and Haversian canals were in close proximity to the implant surface. The buccal side of the implant demonstrated mild to moderate inflammatory infiltrate and signs of hydroxyapatite coating dissolution. These observations suggest that hydroxyapatite coatings can resist degradation in contact with bone but may be more prone to dissolution in contact with soft tissue.

Aged↗
PubMed2005

Kinetics and template nucleation of self-assembled hydroxyapatite nanocrystallites by chondroitin sulfate.

Biomineralization is an important process, which is often assisted by biomolecules. In this paper, the effect of chondroitin sulfate on the crystallization of hydroxyapatite was examined quantitatively based on a generic heterogeneous nucleation model. It is found that chondroitin sulfate can suppress the supersaturation-driven interfacial structure mismatch between the hydroxyapatite crystal and the substrate and promote the formation of ordered hydroxyapatite nanocrystallite assemblies. The nucleation mechanism of self-aligned hydroxyapatite nanocrystallites was examined from the viewpoints of kinetics and interfacial structure and properties, which contributes to an understanding of the fundamentals of biomineralization of self-assembled structures. The results obtained from this study will provide a basic principle to design and fabricate highly orderly organic-inorganic hybrid materials.

Biocompatible Materials↗
PubMed2003

Hard tissue augmentation of the mandibular region with hydroxyapatite granules.

Interventions in the maxillofacial region for either reconstructive or esthetic reasons may sometimes necessitate the augmentation of hard tissues. Although autogenous bone grafts are the first choice, donor site morbidity and difficulties in shaping make alloplastic implants another reliable alternative. Among the alloplastic implants, hydroxyapatite granules, with their high biocompatibility, are a good choice. In a total of 11 patients presenting with mandibular deformities between 1998 and 2002, contour enhancement was performed with the use of hydroxyapatite granules, with a porous structure of 200 microm obtained in prefabricated syringes of 0.8 ml. Follow-up ranging from 3 to 46 months has revealed that the desired contours were established without any significant volume loss. No complications regarding the use of hydroxyapatite granules were encountered. Hydroxyapatite granules heal by allowing fibrovascular tissue ingrowth, do not cause foreign body reactions, and offer ease in use and shaping. These advantages make them a comfortable and reliable choice in maxillofacial hard tissue augmentation procedures in general and in mandibular deformity corrections in particular.

Adult↗
PubMed1998

The synthetic hydroxyapatite implant: a report on 65 patients.

Sixty-five patients receiving the FCI synthetic hydroxyapatite implant (FCI3, FCI, Issy-Les-Moulineaux, France) after enucleation, evisceration, or as a secondary implant were studied under human trial guidelines established by Health and Welfare Canada. The implant is chemically identical to the original coralline Bio Eye (Integrated Orbital Implants Inc., San Diego, CA, U.S.A.), is easy to work with, and was implanted without difficulty using a wrap of polygalactin 910 (Vicryl mesh, Ethicon, Inc.) in the majority of patients. Postoperative drilling was carried out at approximately 6 months and found to be much easier than drilling of the Bio Eye. The implant could be hand drilled using drill bits rolled between the thumb and index finger. Postoperatively, patients were followed-up from 7 to 24 months and did not have any problems different from those associated with the original hydroxyapatite implant derived from sea coral (Bio Eye). One case of conjunctival dehiscence occurred at 4 weeks and required a temporalis fascia patch graft to repair. One implant became infected after drilling and had to be removed. The motility obtained with the third-generation FCI implant (FCI3) was similar to that seen with the Bio Eye, in comparable patients. That is, those receiving implants after an evisceration, on the whole, had better motility than those receiving an implant after primary enucleation or secondary implantation. The FCI3 hydroxyapatite implant is a viable alternative to the original Bio Eye hydroxyapatite implant. It's advantages are: 1) reduced cost, and 2) ease of drilling (a motorized drill is not required). The implant was given Health and Welfare approval in Canada on February 26, 1997.

Biocompatible Materials↗
PubMed1998

Postimplantation density changes in coralline hydroxyapatite orbital implants.

The purpose of our study was to determine serial mineral density changes in coralline hydroxyapatite orbital implants after implantation into the human socket. Prospective analysis by quantitative computed tomography determined the mineral density of hydroxyapatite orbital implants in five patients before and at two time intervals after implantation. Mineral density of the spheres increased an average of 135% after implantation (3-8 months) from preoperative measurements. The density continued to rise an average of 5% (range, -9%-16%) at the second postoperative period (22-39 months). Average follow-up was 30 months. The increased density in the nonevisceration patients was noted in the regions of the scleral windows and the exposed posterior implant where the cornea had been removed from the scleral wrap. The mineral density of hydroxyapatite spheres markedly increases after implantation. Approximately 2 to 3 years later, the densities continue to increase slightly in enucleation and secondary implant cases. An evisceration implant was the only implant to lose density. This study shows no decrease in the mineral density of orbital coralline hydroxyapatite enucleation implants, suggesting a lack of implant mineral resorption.

Adult↗
PubMed1995

Quantitative measurement of vascularization and vascular ingrowth rate of coralline hydroxyapatite ocular implant by Tc-99m MDP bone imaging.

Complete fibrovascular ingrowth of the hydroxyapatite ocular implant is necessary for peg drilling, the secondary procedure that couples the mobile sphere to the ocular prosthesis providing it with motility. This study was conducted to determine the usefulness of the bone scan for the evaluation and relative quantification of the vascularization of coralline hydroxyapatite ocular implants. In 23 patients (32 scans), vascularization of the ocular implant was measured by three-phase bone scintigraphy. There were 16 patients with left, and 7 with right orbital implants. At followup 0.5 to 8 months after successful hydroxyapatite implantation, the mean implant to normal intraorbital activity ratio on delayed bone scans in anterior view was 2.73 +/- 0.73 (mean +/- SD) with a range of 1.42-4.2. The normal right to left and left to right intraorbital bone activity ratios determined in anterior view from 10 normal delayed bone scans were 0.98 +/- 0.05 (mean +/- SD) and 1.02 +/- 0.05 (mean +/- SD) respectively, with a range of 0.93-1.07. The difference of the activity (count) ratios among the successfully implanted group and normals was statistically significant (P < 0.0001). A hydroxyapatite ocular implant to contralateral intraorbital bone activity ratio of greater than 1.12 with a homogeneous tracer distribution throughout the implant suggests adequate and diffuse vascularization is present. The progressive increase in activity ratio of the orbital implants seen in the early postimplantation period, which is indicative of the progression of vascularization, reaches a plateau after 1 month and remains relatively stable thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗